import pygame
from pygame.sprite import Group
import sys
from settings import Settings
from ship import Ship
from alien import Alien
from bullet import Bullet
from time import sleep
from button import Button

def get_number_aliens_x(ai_settings, alien_width):
    """计算每行可容纳多少个外星人"""
    available_space_x = ai_settings.screen_width - 2 * alien_width 
    number_aliens_x = int(available_space_x / (2 * alien_width))
    return number_aliens_x 

def get_number_rows(ai_settings, ship_height, alien_height):
    """计算屏幕可容纳多少行外星人"""
    available_space_y = (ai_settings.screen_height -
        (3 * alien_height) - ship_height)
    number_rows = int(available_space_y / (2 * alien_height)) 
    return number_rows 

def create_alien(ai_settings, screen, aliens, alien_number, row_number): 
    """创建一个外星人并将其放在当前行"""
    alien = Alien(ai_settings, screen)
    alien_width = alien.rect.width
    alien.x = alien_width + 2 * alien_width * alien_number
    alien.rect.x = alien.x
    alien.rect.y = alien.rect.height + 2 * alien.rect.height * row_number 
    aliens.add(alien)

def fire_bullet(ai_settings, screen, ship, bullets):
    """如果还没有到达限制，就发射一颗子弹"""
    
    if len(bullets) < ai_settings.bullets_allowed:
        new_bullet = Bullet(ai_settings, screen, ship)
        bullets.add(new_bullet) 

def check_fleet_edges(ai_settings, aliens):
    """有外星人到达边缘时采取相应的措施"""
    for alien in aliens.sprites():
        if alien.check_edges():
            change_fleet_direction(ai_settings, aliens)
            break


def change_fleet_direction(ai_settings, aliens):
    """将整群外星人下移，并改变它们的方向"""
    for alien in aliens.sprites():
        alien.rect.y += ai_settings.fleet_drop_speed
    ai_settings.fleet_direction *= -1 


def check_keydown_events(event, ai_settings, screen, ship, bullets):
    """响应按键"""
    if event.key == pygame.K_RIGHT:
        ship.moving_right = True
    elif event.key == pygame.K_LEFT:
        ship.moving_left = True
    elif event.key == pygame.K_SPACE:
        fire_bullet(ai_settings, screen, ship, bullets)
    elif event.key == pygame.K_q:
        sys.exit() 


def check_keyup_events(event, ship):
    """响应松开"""
    if event.key == pygame.K_RIGHT:
        ship.moving_right = False
    elif event.key == pygame.K_LEFT:
        ship.moving_left = False

def check_play_button(ai_settings, screen, stats, sb, play_button, ship,
    aliens, bullets, mouse_x, mouse_y):
    """玩家单击Play按钮时开始新游戏"""
    button_clicked = play_button.rect.collidepoint(mouse_x, mouse_y)
    if button_clicked and not stats.game_active:
        
        ai_settings.initialize_dynamic_settings() 
        
        pygame.mouse.set_visible(False) 
        
        stats.reset_stats()   
        stats.game_active = True 

        
        sb.prep_score()
        sb.prep_high_score()
        sb.prep_level() 
        sb.prep_ships()   

        
        aliens.empty()
        bullets.empty()

        
        create_fleet(ai_settings, screen, ship, aliens)
        ship.center_ship() 

def check_bullet_alien_collisions(ai_settings, screen, stats, sb, ship,
    aliens, bullets): 
    """响应子弹和外星人的碰撞"""
    
    collisions = pygame.sprite.groupcollide(bullets, aliens, True, True)
    
    if collisions:
        for aliens in collisions.values():
            stats.score += ai_settings.alien_points * len(aliens)
            sb.prep_score() 
        check_high_score(stats, sb)
    if len(aliens) == 0:
        
        bullets.empty()
        
        ai_settings.increase_speed()

        
        stats.level += 1
        sb.prep_level()
        
        create_fleet(ai_settings, screen, ship, aliens) 

def check_aliens_bottom(ai_settings, screen, stats, sb, ship, aliens, 
    bullets):
    """检查是否有外星人到达了屏幕底端"""
    screen_rect = screen.get_rect()
    for alien in aliens.sprites():
        if alien.rect.bottom >= screen_rect.bottom:
            
            ship_hit(ai_settings, screen, stats, sb, ship, aliens, bullets)
            break  

def create_fleet(ai_settings, screen, ship, aliens):
    """创建外星人群"""
    
    alien = Alien(ai_settings, screen)
    number_aliens_x = get_number_aliens_x(ai_settings, alien.rect.width)
    number_rows = get_number_rows(ai_settings, ship.rect.height,
        alien.rect.height) 

    
    for row_number in range(number_rows):
        for alien_number in range(number_aliens_x):
            create_alien(ai_settings, screen, aliens, alien_number,
                row_number) 

def ship_hit(ai_settings, screen, stats, sb, ship, aliens, bullets):
    """响应被外星人撞到的飞船"""
    if stats.ships_left > 0: 
        
        stats.ships_left -= 1

        
        sb.prep_ships() 

        
        aliens.empty()
        bullets.empty() 

        
        create_fleet(ai_settings, screen, ship, aliens)
        ship.center_ship()

        
        sleep(0.5)
    else:
        stats.game_active = False
        pygame.mouse.set_visible(True)

def check_high_score(stats, sb):
    """检查是否诞生了新的最高得分"""
    if stats.score > stats.high_score:
        stats.high_score = stats.score
        sb.prep_high_score() 

def check_events(ai_settings, screen, stats, sb, play_button, ship, aliens,
    bullets):   
    """响应按键和鼠标事件"""
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            sys.exit()
        elif event.type == pygame.KEYDOWN:                                     
            check_keydown_events(event, ai_settings, screen, ship, bullets)
        elif event.type == pygame.KEYUP:
            check_keyup_events(event, ship)
        elif event.type == pygame.MOUSEBUTTONDOWN:
            mouse_x, mouse_y = pygame.mouse.get_pos()
            check_play_button(ai_settings, screen, stats, sb, play_button,
                ship, aliens, bullets, mouse_x, mouse_y)  

def update_bullets(ai_settings, screen, stats, sb, ship, aliens, bullets):
    """更新子弹的位置，并删除已消失的子弹"""
    
    bullets.update() 
 
    
    for bullet in bullets.copy():
        if bullet.rect.bottom <= 0:
            bullets.remove(bullet)

    
    check_bullet_alien_collisions(ai_settings, screen, stats, sb, ship,
        aliens, bullets) 

def update_aliens(ai_settings, screen, stats, sb, ship, aliens, bullets): 
    """
    检查是否有外星人位于屏幕边缘，并更新整群外星人的位置
    """
    check_fleet_edges(ai_settings, aliens)
    aliens.update() 

    
    if pygame.sprite.spritecollideany(ship, aliens):
        ship_hit(ai_settings, screen, stats, sb, ship, aliens, bullets) 

    
    check_aliens_bottom(ai_settings, screen, stats, sb, ship, aliens, bullets) 

def update_screen(ai_settings, screen, stats, sb, ship, aliens, bullets,
    play_button):  
    """更新屏幕上的图像，并切换到新屏幕"""
    
    screen.fill(ai_settings.bg_color)
    
    for bullet in bullets.sprites():
        bullet.draw_bullet()
    
    ship.blitme()
    
    aliens.draw(screen)       
    
    sb.show_score()

    
    if not stats.game_active:
        play_button.draw_button()
    
    pygame.display.flip()

